Electrically insulated copper strip conductors



y 67 E. H.0LSON 3,317,876

'ELECTRICALLY INSULATED COPPER STRIP CONDUCTORS Filed Sept. 14, 1964 FIG. I

FIG. 2

INVENTOR. EMIL HARRY OLSON ATTORNEYS United States Patent 3,317,876 ELECTRICALLY INSULATED COPPER STRIP CONDUCTORS Emil H. Olson, Muslregon, Mich., assignor to Anaconda Wire and Cable Company, a corporation of Delaware Filed Sept. 14, 1964, Ser. No. 396,087 Claims. (Cl. 3362tl6) This invention relates to electrically insulated copper strip conductors for use in the manufacture of electrical coils. More particularly, it is directed to a method of manufacturing electrically insulated copper strip conductors which are characterized by metallic aluminum along the side edges of the strip and have a dielectric oxidic coating on the metallic aluminum. The invention further relates to electrical strip conductors made according to the method, and to the manufacture of electrical coils from the electrically insulated copper strip conductors.

In the manufacture of insulated copper magnet strip conductors which are most commonly used for the manufacture of electrical coils, it is essential that the insulating coatings which are applied to the copper strip be free from discontinuities which might cause short circuits in their electrical application. The most common source of these discontinuities in the insulating coating has been found to occur along the side edges of the strip conductor. These side edges are the most common source of failings both because they are so diflicult to coat properly with insulating varnishes or lacquers and also because they present such a relatively sharp edge that the insulating coatings either do not adhere properly or they become scraped off during handling, such as the winding operation required to form electrical coils.

In forming the narrow copper strips in the fabrication of the strip conductors, the method almost universally followed is to cut the narrow copper strip from a much wider copper strip. When this wide copper strip is cut longitudinally into narrower strips the cutting operation always exposes the side edge portions of the narrower strips and leaves them rough with slivers and burrs. Thus, even if the wider copper strips are coated with a dielectric insulating coating before the cutting operation, the flat surfaces may :be adequately insulated but the side edge portions must be covered over with a suitable insulation or they would surely be the source of a short circuit particularly in their use of electrical coils.

It is an object of this invention to provide an electrical strip conductor which is insulated along its side edge portions with an insulation which is continuous throughout its length and is resistant to removal by abrasion during handling. It is also an object of the invention to provide continuous methods for the manufacture of these electrically insulated strip conductors.

The method is one for making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges. According to the invention, the side edges of the narrow strips are cleaned and deburred and metallic aluminum is applied to the side edges. The strip is then treated to form a continuous oxidic dielectric film on the metallic aluminum along the side edges to cover and insulate the side edges of the strip. An electrical insulating film coating is also provided on at least one of the flat surfaces of the strip. It is clear that by the method of the invention in which the side edges of metallic aluminum are first coated, the subsequent formation of an oxidic dielectric film is easily made to the metallic aluminum and a strong and continuous insulating film along the side edge portions of the strip conductor is assured. The coating of the flat surfaces of the strip conductor can be made either before the strip conductor has been longitudinally cut from a wider copper strip or it can be made subsequent to the formation of the dielectric oxidic film along the side edges of the strip.

The metallic aluminum can be applied to the side edges of the strip either by passing the strip continuously through an aluminum coating operation or the copper strip can be wound into a roll and coated with aluminum along its side edges in a batch process. For the formation of the dielectric oXidic film on the aluminum along the side edges, however, it is preferred first to wind the copper strip into roll form with a sealant between the turns of the roll and then immerse the roll into an aqueous electrolytic oxidation bath to form an anodic dielectric film on the metallic aluminum which is contained on the side edges of the copper strip. Once the copper strip conductor has been coated on its side edges with the oxidic dielectric film, and provided at least one of the fiat surfaces is coated with an electric insulating film, the electrically insulated copper strip conductor can be unwound from the roll and then wound into an electrical coil.

The electrically insulated copper strip conductor which is formed according to the method of the invention consists of a copper strip with a metallic aluminum coating on at least the sides of the strip. An oxidic dielectric film is formed on the aluminum coating and covers and insulates the side edges of the strip, and an electric insulating film is provided on at least one flat surface of the strip. The electrical coil is formed from an extended length of the electrically insulated copper strip conductor as described and has the electric insulating film on the flat surface of the conductor disposed between successive layers of the coil.

A preferred embodiment of the invention described hereinbelow with reference to the drawing wherein:

FIG. 1 is a side elevation, partly schematic, of a first method of forming electric strip conductors;

FIG. 2 is a side elevation, partly schematic, of a second method of forming electric strip conductors; and

FIG. 3 is a section of a copper strip conductor formed according to the methods in FIGS. 1 and 2.

As shown in FIG. 1 a coil 10 comprising a multiplicity of turns of a flat strip of copper 11, which has been cut from a wider copper strip, is being fed to a first cleaning and deburring station 12 where the side edge portions 13 of the strip 11 are being cleaned of slivers and burrs by means of vertical rolls 14 and horizontal rolls .15. By these mechanical means or their equivalent, the sharp cutting edges of the strip 11 are rounded and relatively smooth side edges are prepared by this mechanical treatment and with the assistance of a chemical treatment if required. The cleaned and deburred copper strip 11 is then passed to chamber 16 where metallic aluminum is disposed only on the side edges of the copper strip. Protective plates 17 and 18 are positioned substantially against the flat surfaces of the strip 11 to protect these fiat surfaces from aluminum deposition. These protective plates should be of a material such as plastic, wood or fiber. In applying the aluminum coating 19 on the side edges of the strip the coating generally disposed not only along the side edge portions of the strip but also along a small marginal edge portion of the fiat surfaces of the strip as will be seen in FIG. 3. Thus, in FIG. 1 as the copper strip 11 emerges from the aluminum coating chamber 16 the strip 11 appears to have a greatly enlarged thickness and this has been done to illustrate that an aluminum coating 19 has been disposed on the side edges of the strip and on a small marginal portion of the flat surfaces of the strip.

The copper strip with the aluminum disposed on its side edges is then passed to a coating station 20 where an organic insulating film such as epoxy, 'Formvar, polyester, polyurethane, polyamide, polyimide, polyamidepolyimide, or any of the standard materials now used for coating magnet conductors, is applied to the fiat surfaces of the strip 11 between the aluminum deposit 19 on the side edges thereof.

The thus coated strip conductor is then wound into a roll while a thin plastic sheet 21 is simultaneously fed with the strip conductor 11 so that the roll is interleaved with this thin plastic sheet 21 between successive turns. Polyethylene sheets have been used with success for this operation and it has been found that the rolls can also be interleaved with another sealant such as a heavy liquid like kerosene.

The roll 22 and others like it are then taken to anodizing equipment where they are lowered into an electrolytic bath 23 which may be chromic, sulfuric, oxalic or other acid or it may be a caustic alkaline bath. Low voltage direct current is then passed through the bath with each of the rolls therein serving as the anode. A lead stainless steel or other conducting electrode is employed as the cathode. A film of aluminum oxide is thereby formed on any aluminum surface exposed to the electrolyte and thus all exposed aluminum edges defining the flat sides of the rolls are covered with an even and continuous insulating anodic film.

The plastic sheet 21 which is interleaved between the turns of the roll serves as a sealant to prevent the electrolyte from penetrating between the turns of the roll by capillary action where if it remains it might corrode the copper if it were to contact the metal or it would attack the organic coating which has previously been applied to the fiat surfaces of the strip conductor. After the anodizing has been completed the batch of rolls are lifted from the bath, rinsed and dried and the strip conductor is then prepared to be rewound from the roll into electrical coils to which leads may be attached.

Referring now to FIG. 2 a second embodiment of the method of the invention is shown schematically. A roll 25 of bare copper strip conductor which has been cut from a wider copper strip but has had no prior treatment is interleaved with a sealant, either a thin plastic sheet or a heavy liquid. The roll 25 is immersed into an etching solution in bath 26 to clean the edges and remove burrs,

slivers and sharp corners along the side edges of the nar-- row copper strip. The sealant will prevent the solution in the bath from being drawn between the turns of the roll by capillary action and will maintain the flat surfaces free from this etching operation. The etched roll 25 is then removed from the bath 26 and is moved to a chamber 27 where the roll 25 is placed and the side edges of the entire interleaved coil for metallic aluminum deposit thereon by any of the presently known methods such as vapor deposition, plating, cladding or perhaps an electrochemical process. The roll 25 is then passed to an anodizing bath 28 where the aluminum coated side edges can be anodized to form an anodic dielectric film on the aluminum side edges by immersing the roll 25 into the electrolyte in a similar operation as that described in relation to FIG. 1. A copper strip conductor 29 is then unwound from the roll 25 and is passed through a coating die 30 Where any of the organic insulating films mentioned above are coated either on one flat surface of the strip conductor, both flat surfaces, or on the entire conductor.

The conductor 29 is then passed to a coil winding operation where the extended length of copper strip conductor is wound into a multilayer coil with the organic electric insulating film disposed Within successive layers of the coil, and then suitable leads are attached.

It is also proposed that the copper strip conductor can be formed by coating the entire copper strip with metallic aluminum coating and then anodizing the entire aluminum coated copper strip.

As shown in FIG. 3 the electrically insulated copper strip conductor consists of a copper strip 31 which has a top flat surface 32 and a bottom flat surface 33 and flat side edge portions 34 and 35. A metallic aluminum coating is deposited on the flat side edges 34 and 35 and extends continuously beyond the side edges and covers the marginal edge portions 36, 36, 37 and 37 on both of the fiat surfaces up to about 10 percent of the flat surface area. A thin organic insulating film 38 and 39 is deposited on the fiat surface of the copper strip conductor between the aluminum side edge deposits 36, 36', 3'7 and 37.

I claim:

1. An electrically insulated copper strip conductor comprising:

(a) a copper strip,

(b) a metal aluminum coating on the side edge portions of the strip,

(0) an oxidic dielectric film on the aluminum coating covering and insulating the side edges of the strip, and

(d) an electric insulating film on at least one flat surface of the strip.

2. An electrically insulated copper strip conductor com prising:

(a) a copper strip, I

(b) a metal aluminum coating on at least one of the side edges of the strip,

(c) a continuous anodic dielectric film formed on the aluminum coating covering and insulating the side edges of the strip, and

(d) an electric insulating film on at least one of the flat surfaces of the strip.

3. An electrically insulated copper strip conductor comprising:

(a) copper strip which is bare of any coating at its side edges,

(b) a metal aluminum coating on the side edges of the copper strip,

(c) a continuous anodic dielectrim film formed on the aluminum coating covering and insulating side edges of the strip, and

(d) an organic electric insulating film on at least one flat surface of the strip.

4. An electric coil comprising:

(a) an extended length of copper strip wound into a multi-layer coil,

(b) a metal aluminum coating on at least the side edges of the strip,

(c) an oxidic dielectric film on the aluminum coating covering and insulating the side edges of the strip, and

(d) an electric insulating film on at least one fiat surface of the strip and disposed between successive layers of the coil.

5. An electric coil comprising:

(a) an extended length of copper strip wound into a multi-layer coil,

(b) a metal aluminum coating on the side edges of the copper strip,

(0) a continuous anodic dielectric film formed on the aluminum coating covering and insulating the side edges of the strip, and

(d) an organic electric insulating film on at least one flat surface of the strip and disposed between successive layers of the coil.

References Cited by the Examiner UNITED STATES PATENTS 1/1955 Flynn 174-110.1 8/ 1961 Worcester 336206 X FOREIGN PATENTS 279,876 10/1927 Great Britain. 

1. AN ELECTRICALLY INSULATED COPPER STRIP CONDUCTOR COMPRISING: (A) A COPPER STRIP, (B) A METAL ALUMINUM COATING ON THE SIDE EDGE PORTIONS OF THE STRIP, (C) AN OXIDIC DIELECTRIC FILM ON THE ALUMINUM COATING COVERING AND INSULATING THE SIDE EDGES OF THE STRIP, AND (D) AN ELECTRIC INSULATING FILM ON AT LEAST ONE FLAT SURFACE OF THE STRIP. 